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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7bc0cf13b15e3c874d374daa29ac892d6accc8dce9d2548740aa268e65c7378' 
  AND token = '3gdTQibOcrGv2rOI4A4gWn8w1GFR0DdM6NhUjJbG/3s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}